Concentrated liquid hard surface cleaners which are suitable for dilution with tap water have advantages over ready-to-use hard surface cleaners. Dilutable concentrates are typically less expensive to manufacture and ship, require less storage space prior to dilution and impose a lower burden on landfill operations since less packaging is involved.
Development of such dilutable liquid concentrates presents unique problems. First, they should contain a sequestering agent or crystallization inhibitor that will help prevent precipitation of insoluble salts of polyvalent metal cations present in hard water diluents. At the typically basic pH of concentrated hard surface cleaners, the polyvalent metal cations react with carbonates and other anionic species in the tap water and precipitate. Sequestering agents, however, tend to promote spotting/filming on the surfaces being cleaned. Accordingly, it has been difficult to formulate a dilutable concentrated liquid hard surface cleaner that contains sufficient sequestering agents but does not promote excessive spotting/filming.
Second, the sequestering agent should be soluble in both the liquid concentrate and aqueous dilutions thereof over a wide range of concentrations. Sequestering agents typically require carboxylate or phosphate groups to interact with hardness ions and are soluble in dilute aqueous solutions because of the interactions between water and the highly-charged sequestering moieties in these molecules. However, concentrated dilutable cleaning solutions that contain high levels of non-aqueous cleaning solvents pose a problem in getting adequate solubility of the sequestering agents. Sequestrants are typically much less soluble because they do not effectively interact with the solvents to maintain solubility. For example, polycarboxylate sequestrants that are soluble in water are typically not very soluble in non-aqueous solvents because of the relatively high charge density in these polycarboxylate sequestrants compared to the non-aqueous cleaning solvents. This limits the amount of sequestrant that can be added to a concentrated hard surface cleaning composition. In regions where the water is very hard, this raises the real risk that there will be insufficient sequestrant to prevent precipitation of hardness ions in the diluted cleaner, with the result that precipitated salts will form in the diluted cleaning solution, and plug the sprayer used to deliver the cleaning solution to the surface to be cleaned.
Given the forgoing, there is a continuing need to provide dilutable concentrates for use as hard surface cleaners that will remain stable for prolonged periods when diluted with hard or de-ionized water and which will not promote spotting/filming. It is therefore an object of this invention to provide such a product by utilizing a maleic acid-olefin copolymer as a crystallization inhibitor in a concentrated liquid detergent composition.